Electrical resistor



April 30, 1963 B. soLow 3,088,085

ELECTRICAL RESISTOR Filed Nov. 2'7, 1959 m 20 m g 1% a j/il/ IN VEN TOR.

BENJAMIN; s04 0w ATTOKA/EY ferred; it being understood, however,

United States Patent i 3,088,085 ELECTRICAL RESISTOR Benjamin Solow,North Hollywood, Calif., assiguor to International Resistance Company,Philadelphia, Pa. Filed Nov. 27, 1959, Scr. No. 855,804 Claims- (Cl.338-283) The present invention relates to an electrical resistor, andmore particularly to a miniaturized, film type electrical resistor.

The present trend in the electrical industry is toward miniaturizedelectrical components. Another trend in the electrical industry is tothe use of printed circuit boards on which the electrical components aremounted. For use on the printed circuit boards, the electricalcomponents should be as small as possible to take up as little room aspossible on the board, and the terminals of the components should bearranged for ease of mounting the components on the board.

A problem in the manufacture of electrical resistors of the typecomprising a film of a resistance material coated on an insulating baseis to achieve a desired resistance value, and particularly highresistance values. The resistance value of a film of resistance materialcan be varied by varying the composition of the resistance material, thethickness of the film, and/or the length of the film. Decreasing thethickness and/ or increasing the length of the film increases theresistance value. Varying the composition of the resistance film isimpractical since there are not many materials which have stableelectrical resistance characteristics. Varying the thickness of the filmis not satisfactory alone since the thickness is difficult to control toachieve a desired value. Therefore, it has been found preferable tocombine varying the length of the film along with a variation ofthickness to achieve various resistance values.

Most film type electrical resistors use a cylindrical insulating base onwhich the resistance material is coated. The length of the resistancematerial is varied by cutting a spiral groove through the resistancelayer to achieve a resistance path which extends helically around thebase. By varying the pitch of the spiral groove, the length of thehelical resistance path is varied. This also varies the width of thepath which also changes the resistance value. Thus, by cutting a grooveof a proper length, a resistance path of a desired resistance value canbe accurately obtained.

With the trend to miniaturized components, the use of spiraling to varythe resistance value of a film type resistor has become lesssatisfactory. The smaller the size of the resistor, the more difficultit is to cut a fine enough spiral groove to achieve any major change inthe resistance value. Also, the resistors using cylindrical bases havetheir terminals extending longitudinally from the ends of the base. Inorder for such resistors to be mounted on a printed circuit board, theterminals must be bent and shaped to be inserted into holes in theboard.

It is an object of the present invention to provide a novel electricalresistor.

It is another object of the present invention to provide a novelminiaturized electrical resistor.

It is still another object of the present invention to provide aminiaturized electrical resistor the resistance value of which can beeasily varied and adjusted to a predetermined close percentagetolerance.

It is a further object of the present invention to provide aminiaturized electrical resistor which can be easily mounted on aprinted circuit board.

Other objects will appear hereinafter.

For the purpose of illustrating the invention there is shown in thedrawings forms which are presently prethat this invention 3,088,085Patented Apr. 30, 1963 ice FIGURE 1 is a top elevational view of a basefor the resistor of the present invention.

FIGURE 2 is a side elevational view of the base of the resistor of thepresent invention with the terminals attached thereto.

FIGURE 3 is a sectional FIGURE 2.

FIGURE 4 is a view similar to FIGURE 3 with the resistance materialcoated on the base.

FIGURE 5 is a view similar to FIGURE 4 showing the manner of varying theresistance value of the resistor.

FIGURE 6 is a sectional view similar to FIGURE 5 showing the completedresistor.

FIGURE 7 is a bottom elevational view of the completed resistor of thepresent invention.

FIGURE 8 is a top elevational view of a modification of the resistor ofthe present invention.

FIGURE 9 is a side elevational view of the modification of the resistorof the present invention.

Referring initially to FIGURES l-7, the resistor of the presentinvention is generally designated as 10.

Resistor 10 comprises a substantially rectangular base 12 of a hard,electrical insulating material, such as a ceramic or glass. The topsurface of the base 12 is provided with a V-shaped groove 14 whichextends back and forth from end-to-end of the base 12 in a continuous,sinuous path. The ends 14a and 14b of the groove 14 are adjacentopposite sides of the base 12 (see FIGURE 1). Each straight section ofthe groove 14 is spaced from the adjacent straight sections of thegroove 114 by a ridge 16. The base 12 is provided with a pair of spaced,blind holes 18 in the bottom surface of the base 12.

A separate terminating stripe 20 is coated on the outer side of each ofthe ridge portions 161: and 16b just beyond the ends 14a and 14b of thegroove 14. Each of the terminating stripes 20 extends downwardly alongthe adjacent side of the base 12, along the bottom surface of the base12 to an adjacent blind hole 18, and then upwardly along a portion ofthe hole 18 (see FIGURE 3). The terminating stripes 20 are layers of anelectrically conductive ma terial, such as gold or silver, which ispainted, sprayed or otherwise applied to the base 12.

A layer 22 of an electrical resistance material is coated over theentire top surface of the base 12 (see FIGURE 4). The layer 22 may be ofany of the well known type resistance materials, such as carbon or metalparticles mixed with a plastic binder, pure carbon, carbon mixed with ametal, or a pure metal or metal alloy. The resistance layer 22 may beapplied to the base 12 by either painting, spraying paralytic depositionfirom a gas or vapor, or by deposition from an evaporated vapor in avacuum. The resistance layer 22 extends across the portions of both ofthe terminating strips 20 which are on the ridge portions 16a and 16b.Thus, the resistance layer '22 is electrically connected to theterminating strips 20.

A separate terminal wire 24 of an electrical conductive metal isinserted in each of the blind holes 18 in the base 12. The terminalwires 24 are each secured in the holes 18 by a layer of an electricallyconductive cement 26 which surrounds the end portion of the terminalwires 24 which are within the holes 18. The conductive cement 26 may bea plastic cement having metallic particles therein, or may be a solder.The conductive cement 26 not only physically secures the teminal wires24 in the holes 18, but also electrically connects the terminal wires 24to the terminating strips 20. Thus, the terminal wires 24 are eachelectrically connected to the resistance layer 22 through the conductivecement 26, and the terminating strip 20. The terminal wires 24 may besecured to the base 12 either before or after the resistance view takenalong line 3-3 of easily adjusted to obtain a desired resistance value.

After the resistance value of the resistance layer 22 is adjusted to thedesired value, a protective jacket 28 of an electrical insulatingmaterial can be provided around the base 12, as shown in FIGURE 6. Theprotective jacket 28 may be coated, molded, or cast around the base 12and across the resistance layer 22, leaving the terminal from the base12, and are parallel, the resistor of the present invention can beeasily mounted on a printed circuit board by inserting the terminals 24through holes in the board.

Referring to FIGURES 8 and 9, a modification of the resistor of thepresent invention is generally designated as 30.

Resistor 30 comprises a substantially rectangular base 32 of a hard,electrical insulating material, such .as a ceramic or glass. The topsurface of the base 32 is provided with a V-shaped groove 34 whichextends from side-to-side of the base 32 in a continuous, sinuous pat-The terminal wires 40 which are electrically connected I claim:

1. An electrical resistor comprising a substantially recangular base ofan electrical insulating material, said base having a sinuous groove inits upper surface, said groove extending from side-to-side of said basewith one and the resistance material is coated on only the sides of thegroove.

4. An electrical resistor in accordance with claim 3 in which t pair ofspaced blind holes in its bottom surface, said groove being V-shape intransverse cross-section and extending back and forth across the topsurface of the base to the conductive stripes so as to electricallyconnect each path.

References Cited in the file of this patent UNITED STATES PATENTSStoekle June 24, 1930 6 Goeppinger et a1 June 21, 1955 Anderson et a1.June 211, 1955 Kohring Apr. 17, 1956 Johnson Dec. 25, 1956 Thias Jan. 8,1957 Pritikin et a1 Dec. 31, 1957

1. AN ELECTRICAL RESISTOR COMPRISING A SUBSTANTIALLY RECTANGULAR BASE OFAN ELECTRICAL INSULATING MATERIAL, SAID BASE HAVING A SINUOUS GROOVE INITS UPPER SURFACE, SAID GROOVE EXTENDING FROM SIDE-TO-SIDE OF SAID BASEWITH ONE END OF THE GROOVE BEING AT ONE END OF THE BASE AND THE OTHEREND OF THE GROOVE BEING AT THE OTHER END OF THE BASE, SAID BASE HAVINGAT LEAST THREE BLIND HOLES IN ITS BOTTOM SURFACE, TWO OF SAID HOLESBEING ADJACENT OPPOSITE ENDS OF SAID BASE, A LAYER OF AN ELECTRICALRESISTANCE MATERIAL COATED ON THE SURFACE OF SAID GROOVE TO PROVIDE ANELONGATED SINUOUS RESISTANCE PATH, A SEPARATE TERMINAL WIRE OF ANELECTRICAL CONDUCTING MATERIAL SECURED IN AND PROJECTING FROM EACH OFSAID HOLES, AND MEANS EXTENDING ALONG THE SURFACE OF SAID BASE ANDELECTRICALLY CONNECTING EACH OF SAID TERMINAL WIRES TO SAID RESISTANCEPATH, TWO OF SAID TERMINAL WIRES BEING ELECTRICALLY CONNECTED TOOPPOSITE ENDS OF THE RESISTANCE PATH, AND THE OTHER OF SAID TERMINALWIRES BEING CONNECTED TO SAID RESISTANCE PATH BETWEEN THE ENDS OF THERESISTANCE PATH.